Electrolysis solution for electrolytic capacitors

ABSTRACT

An electrolysis solution for electrolytic capacitors including an aqueous organic solvent consisting of water and a water-compatible organic solvent and 1,6-decane-dicarboxylic acid or salt thereof dissolved therein. The solution further contains one or more additives selected from dinitriles, pivalic acid and salts thereof, diesters, alkylated lactones, cyanoalkanoic esters, monocarbboxylic acids each having a C 3-7  alkyl chain and substituted with two C 1-4  alkyl groups at the β-position to the carboxyl group and salts thereof, monocarboxylic acids each having C 3-7  alkyl chain and substituted with one ethyl group at the α-position to the carboxyl group and salts thereof, and monocarboxylic acids derived from cyclic saturated compounds each having five or six ring-constituting carbon atoms and salts thereof. When one or more compounds selected from among dinitriles, diesters, alkylated lactones and cyanoalkanoic esters are used as the additives, the 1,6-decanedicarboxylic acid may be replaced by other carboxylic acid.

FIELD OF INVENTION

The present invention relates to an electrolytic solution forelectrolytic capacitors, that is, an electrolytic solution for drivingelectrolytic capacitors. Specifically, the invention relates to anelectrolytic solution composition which is favorably employable as anelectrolytic solution for driving medium-to-high pressure aluminumelectrolytic capacitors.

BACKGROUND OF INVENTION

As the electrolytic solution for driving medium-to-high pressurealuminum electrolytic capacitors, heretofore has been widely employed anelectrolytic solution comprising an aqueous organic solvent comprisingethylene glycol and a small amount of water and boric acid or ammoniumborate (solute) dissolved therein, because this electrolytic solutionshows a high spark voltage (namely, good resistance to a high voltage).However, since the electrolytic solution having such compositionproduces an excessive amount of water by the esterification reaction ofethylene glycol with boric acid, thus produced water is undesirabley aptto react with an aluminum oxide film of the electrode resulting indeterioration of the film or causes undesired increase of the innerpressure due to evaporation of water at a high temperature of higherthan 100° C. Therefore, the electrolytic solution of this type is notsuitably employed at an elevated temperature.

In order to solve the above-mentioned problems, an electrolytic solutionemploying an organic dicarboxylic acid such as adipic acid, sebacicacid, or azelaic acid or a salt thereof in place of boric acid orammonium borate has been proposed and employed in practice. It isproblem, however, that the solubility of the organic dicarboxylic acidin an aqueous organic solvent is low and therefore the resultingsolution sometimes gives precipitation of crystals at a low temperature.Accordingly, the low temperature performances of the capacitor lowers,and it is not suitably employed at a low temperature.

JP-A-60-13293 describes an electrolytic solution for electrolyticcapacitors which contains, as the solute, butyloctane diacid (i.e.,1,6-decanedicarboxylic acid) or a salt thereof. This patent publicationdescribes that the electrolytic solution containing1,6-decanedicarboxylic acid or a salt thereof shows a high spark voltageas well as a high electroconductivity and further a high solubility, andthat the problem of the precipitation of crystals at a low temperatureis solved.

JP-A-61-116815 describes an electrolytic solution for electrolyticcapacitors which contains as the solute a tertiary monocarboxylic acid(such as pivalic acid) or a salt thereof. This patent publicationfurther states that the use of the tertiary monocarboxylic acid or asalt thereof is effective to reduce an internal resistance of anelectrolytic capacitor, increase resistance to a high voltage, andenlarge the range in which the capacitor can be employed.

JP-A-62-241322 describes an electrolytic solution for electrolyticcapacitors having improved temperature characteristics which comprises asolution comprising ethylene glycol and a solute of a monocarboxylicacid having a total carbon atoms of 4 to 8 and an alkyl side chain (suchas isobutyric acid or pivalic acid) or a salt thereof.

JP-A-6-275472 describes that an electrolytic solution comprising asolution which comprises ethylene glycol and a solute combination of atertiary monocarboxylic acid such as pivalic acid and a secondarydicarboxylic acid such as 2,9-dimethylsebacic acid shows a high sparkvoltage and a high electroconductivity and further is chemicallyconverted readily.

JP-A-6-302475 describes that an electrolytic solution comprising asolution which comprises ethylene glycol and a solute combination of atertiary monocarboxylic acid such as pivalic acid and a secondarypolycarboxylic acid such as 2,9-dimethylsebacic acid shows a high sparkvoltage and a high electroconductivity and further is chemicallyconverted readily.

Recently, various electronic apparatuses employing a switching powersupply are generally utilized as home appliances. Therefore, anelectrolytic capacitor to be employed for the electronic apparatuses isdesired to show increased safety. In order to increase safety ofelectrolytic capacitors, it is necessary to further enhance a sparkvoltage (resistance to a high voltage) of the electrolytic solution. Theconventionally employed electrolytic capacitors cannot satisfy therequirement for enhancement of a spark voltage.

Accordingly, a principle object of the invention is to provide anelectrolytic solution for electrolytic capacitors which showsperformances at a practically satisfactory level in theelectroconductivity and easiness of chemical conversion (in theprocedure for producing an insulating oxide film on a metal element suchas aluminum foil which is used as a positive electrode of electrolyticcapacitors) and further shows a high voltage endurance at a voltagehigher than that at which the conventional electrolytic solutionendures.

DISCLOSURE OF INVENTION

The present invention resides in an electrolytic solution comprisingwater and a water-miscible organic solvent, which further contains1,6-decanedicarboxylic acid or a salt thereof and at least one additiveselected from the group consisting of a dinitrile compound, pivalic acidor a salt thereof, a diester compound, a lactone compound having analkyl group, a cyanoalkanoic acid ester, a monocarboxylic acid having analkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4 carbon atomsat the β-position of the carboxyl group, a salt thereof, amonocarboxylic acid having an alkyl chain of 3-7 carbon atoms and oneethyl group at the α-position of the carboxyl group, a salt thereof, amonocarboxylic acid of a cyclic saturated compound having 5 or 6ring-forming carbon atoms, and a salt thereof.

The invention further resides in an electrolytic solution comprisingwater and a water-miscible organic solvent, which further contains acarboxylic acid or a salt thereof and at least one additive selectedfrom the group consisting of a dinitrile compound, a diester compound, alactone compound having an alkyl group, and a cyanoalkanoic acid ester.

The invention furthermore resides in an electrolytic capacitorcomprising a metallic element having an oxide film on a surface thereofand an electrolytic solution in a sealed case, wherein the electrolyticsolution is one of the above-mentioned electrolytic solution of theinvention. A preferred metallic element is an aluminum foil.

The electrolytic capacitors employing the electrolytic solution of theinvention show easy chemical conversion and electroconductivity similarto those shown by the conventionally used electrolytic capacitors of thesame type, while show a high spark voltage (endurable voltage) such as470 V or higher, further 480 V or higher or 490 V or higher by choosinga preferred combination of the additives to be incorporated into theelectrolytic solution. Moreover, a high spark voltage of 500 V or highercan be attained.

DETAILED DESCRIPTION OF INVENTION

The electrolytic solution of the invention is characterized in that1,6-decanedicarboxylic acid or a salt thereof as a first additive andone or more second additives are dissolved in an aqueous organic solventcomprising water and a water-miscible organic solvent.

First, the water-miscible organic solvent which is employed as anorganic solvent of the electrolytic solution of the invention isdescribed.

The conventional electrolytic solution for electrolytic capacitors usesa combination of water and an aqueous organic solvent (i.e.,water-containing organic solvent). In the present invention, variousknown water-miscible organic solvents can be utilized. Examples of thewater-miscible organic solvents include alcohols such as polyhydricalcohols and monoalcohols, diesters, cyanoalkanoic acid esters,lactones, and sulfoxides such as dimethylsulfoxide. The organic solventcan be a mixture of two or more organic solvents. A water-immiscibleorganic solvent can be used in mixture of the water-miscible organicsolvent, provided the resulting mixture is miscible with water.

Examples of the polyhydric alcohols include ethylene glycol, diethyleneglycol, propylene glycol, dipropylene glycol, 1,3-propanediol,1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol,2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, pinacol,2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5pentanediol, glycerol, 1,2,4-butanetriol, trimethylolethane, mannitol,sorbitol, dulcitol, and poly(vinyl alcohol).

Examples of the monoalcohols include 2-methoxyethanol, 2-ethoxyethanol,2-propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol,3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol,1-ethoxy-2-propanol, and 1-methoxy-2-butanol.

Examples of the lactones include γ-butyrolactone, δ-valerolactone, andε-caprolactone.

Particularly preferred are ethylene glycol and a mixture of ethyleneglycol and lactone.

The water content in the aqueous organic solvent generally is 5 wt. % orless, preferably not less than 0.1 wt. % and not more than 4 wt. % interms of the water content in the electrolytic solution.

The first additive for the electrolytic solution of the invention is1,6-decanedicarboxylic acid or its salts (a salt with an organic basesuch as ammonium salt, methylamine salt, dimethylamine salt,trimethylamine salt, ethylamine salt, diethylamine salt, triethylaminesalt, or a quaternary ammonium salt). The electrolytic solution of theinvention preferably has a pH value in the range of 5 to 7, particularlyin the vicinity of 6. The desired pH value can be achieved by adjustinga ratio of 1,6-decanedicarboxylic acid and a salt thereof or employing asalt of 1,6-decanedicarboxylic acid alone.

According to the study conducted by the inventors, it has been foundthat a commercially available 1,6-decanedicarboxylic acid and saltsthereof contains as impurities 1,10-decanedicarboxylic acid or saltsthereof which are produced in the manufacture of 1,6-decanedicarboxylicacid and their salts. Since 1,10-decanedicarboxylic acid has a highmelting point of 130° C. (melting point of 1,6-decanedicarboxylic acidis 65° C.), a mixture containing a large amount of1,10-decancedicarboxylic acid easily precipitates at a low temperatureand lowers the capacitor performance at a low temperature. Further, iteasily causes transesterification with ethylene glycol in theelectrolytic solution and further causes deterioration ofelectroconductivity at a high temperature, and hence causes lowering ofthe capacitor performance. Therefore, the amount of1,10-decanedicarboxylic acid or a salt thereof contained in1,6-decanedicarboxylic acid or a salt thereof preferably is 3 wt. % orless, more preferably 1 wt. % or less, based on the amount of1,6-decanedicarboxylic acid or a salt thereof.

It is difficult to completely remove 1,10-decanedicarboxylic acid and/ora salt thereof, namely impurities, from the commercially available1,6-decanedicarboxylic acid or a salt thereof. The purification by agenerally performed crystallization can give 1,6-decanedicarboxylic acidor a salt thereof containing approx. 5 to 8 wt. % of1,10-decanedicarboxylic acid and/or a salt thereof.

Accordingly, the content of 1,10-decanedicarboxylic acid and/or a saltthereof (impurities) are preferably reduced by the followingpurification method.

A distillation method which comprises steps of esterification of1,10-decanedicarboxylic acid and 1,6-decanedicarboxylic acid, separatingthe resulting 1,6-decanedicarboxylic acid ester by distillation, andsubjecting the distilled ester to hydrolysis to convert it into acarboxylic acid is preferred. The distillation is preferably carried outunder the condition of a reflux ratio of 0.01 to 100, more preferably0.1 to 30. The theoretical plate number preferably is 2 to 90, morepreferably 5 to 50. The distillation can be performed at a reducedpressure or an atmospheric pressure, but preferably at a pressure 0.1 to200 mmHg, more preferably 0.5 to 30 mmHg. The ester can be methyl ester,ethyl ester, propyl ester (linear or branched), or butyl ester (linearor branched). The distillation method is further advantageous in thatgenerally existing low molecular weight (low boiling-point) impuritiesof 1,6-decanedicarboxylic acid such as butyric acid and hexanoic acidcan be simultaneously removed.

The 1,6-decanedicarboxylic acid or a salt thereof is preferably presentin the electrolytic solution in an amount of 0.1 to 50 wt. % so thatgood electroconductivity and voltage endurance can be attained. Morepreferred is 1 to 40 wt. %, most preferred is 1 to 20 wt. %,particularly 1 to 15 wt. % and further 3 to 10 wt. %.

If the second additive is a dinitrile compound, a diester compound, alactone compound having an alkyl group, or a cyanoalkanoic estercompound, the first additive can be a known carboxylic acid or a saltthereof in place of 1,6-decanedicarboxylic acid or a salt thereof. Theknown carboxylic acid or a salt thereof can be chosen from those knownas additives for electrolytic solutions for electrolytic capacitors.Examples are as follows:

5,6-decanedicarboxylic acid, sebacic acid, adipic acid, 3-dodecyladipicacid, 2,9-sebacic acid, azelaic acid, 1,7-octanedicarboxylic acid,benzoic acid, 3,3-dimethylbutanoic acid, 2,2-diisopropylpropanoic acid,2-methylnonane diacid, 2,4-dimethyl-4-methoxycarbonylundecane diacid,2,4,6-trimethyl-4,6-dimethoxycarbonyltridecane diacid,8,9-dimethyl-8,9-dimethoxycarbonylhexadecane diacid, 11-cyanoundecanoicacid, 7-cyanoundecanoic acid, 2-butyl-7-cyanoheptanoic acid; salts withorganic base such as ammonium salt, methylamine salt, dimethylaminesalt, trimethylamine salt, ethylamine salt, diethylamine salt,triethylamine salt, and tertiary ammonium ssalt of the above-mentionedcarboxylic acids.

The above-mentioned carboxylic acid or a salt thereof is preferablycontained in the electrolytic solution in an amount of 0.1 to 50 wt. %,more preferably 1 to 40 wt. %, most preferably 1 to 20 wt. %(particularly 1 to 15 wt. %), so that good electroconductivity andvoltage endurance can be attained.

The second additive to be added to the electrolytic solution of theinvention is one of the below-mentioned compounds. One or more additivescan be dissolved in the electrolytic solution:

a dinitrile compound, pivalic acid or a salt thereof, a diestercompound, a lactone compound having an alkyl group, a cyanoalkanoic acidester, a monocarboxylic acid having an alkyl chain of 3—7 carbon atomsand two alkyl groups of 1-4 carbon atoms at the β-position of thecarboxyl group, a salt thereof, a monocarboxylic acid having an alkylchain of 3-7 carbon atoms and one ethyl group at the α-position of thecarboxyl group, a salt thereof, a monocarboxylic acid of a cyclicsaturated compound having 5 or 6 ring-forming carbon atoms, and a saltthereof.

Details of the second additives are described below.

Dinitrile Compound

As the dinitrile compound, preferred is a dinitrile compound comprisingan alkylene chain of 1 to 12 carbon atoms to which two nitrile groupsare attached. The alkylene chain can be branched or linear. Examples ofthe dinitrile compounds include linear dinitriles such assuccinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane,1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane,1,9-dicyanononane, 1,10-dicyanodecane, and 1,12-dicyanododecane andbranched dinitriles such as tetramethylsuccinonitrile,2-methylglutaronitrile, 2,4-dimethylglutaronitrile,2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane,2,5-dimethyl-2,5-hexanedicarbonitrile, 2,6-dicyanoheptane,2,7-dicyanooctane, 2,8-dicyanononane, and 1,6-dicyanodecane. Mostpreferred is adiponitrile.

The nitrile compound is preferably contained in the electrolyticsolution in an amount of 0.1 to 50 wt. %, more preferably 1 to 40 wt. %,further preferably 1 to 20 wt. %, based on the total amount of theelectrolytic solution.

Pivalic Acid or a Salt Thereof

The pivalic acid is also named trimethylacetic acid which is representedby the formula of (CH₃)₃COOH. A salt thereof (pivalic acid salt) can bea salt with the aforementioned organic base.

The pivalic acid or a salt thereof is preferably contained in theelectrolytic solution in an amount of 1 to 20 wt. %, more preferably 3to 15 wt. %, based on the total amount of the electrolytic solution.

A ratio of pivalic acid (or a salt thereof):1,6-decanedicarboxylic acid(or a salt thereof, first additive) preferably is in the range of 25:75to 90:10, by weight. The total amount of pivalic acid (or a saltthereof) and 1,6-decanedicarboxylic acid (or a salt thereof) preferablyis in the range of 2 to 30 wt. %, particularly 6 to 25 wt. %, based onthe total amount of the electrolytic solution.

It is preferred that pivalic acid or a salt thereof is contained in theelectrolytic solution in combination with the aforementioned nitrilecompound.

Diester Compound

The diester compound preferably is a diester compound having an alkylenegroup of 2-18 carbon atoms (particularly 4-12 carbon atoms). Thealkylene group can be linear or branched. Examples of the diestercompounds include linear esters such as dimethyl succinate, dimethylglutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate,dimethyl azelate, dimethyl sebacate, dimethyl decanedicarboxylate, anddimethyl 1,10-decanedicarboxylate and branched esters such as dimethyltetramethylsuccinate, dimethyl 2-methylglutarate, dimethyl2,4-dimethylglutarate, dimethyl 2,2,4,4-tetramethyl-4-dimethylglutarate,and dimethyl 1,6-decanedicarboxylate. The diester compounds are notlimited to methyl esters having methyl groups at both terminals, and thediester compounds can be ethyl ester, propyl ester, or phenyl ester.

The diester compound is generally contained in the electrolytic solutionin an amount of 0.01 to 50 wt. %, preferably 0.1 to 40 wt. %, morepreferably 1 to 20 wt. %, based on the total amount of the electrolyticsolution.

In the case that the above-mentioned diester compound is incorporatedinto the electrolytic solution, 1 to 20 wt. % of pivalic acid or a saltthereof is preferably added.

Lactone Compound Having an Alkyl Group

As the lactone compound having an alkyl group, preferred are lactonecompounds having alkyl group of 1 to 12 carbon atoms such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl. The alkyl groupcan be a branched alkyl group such as isopropyl or isobutyl. Morepreferred are lactone compounds having an alkyl group of 4-8 carbonatoms.

Examples of the preferred lactone compounds include γ-nonanolactonehaving one linear pentyl and γ-undecanolactone having one linear heptyl.A δ-lactone compound and an ε-lactone compound can be also employed.

The lactone compound is generally contained in the electrolytic solutionin an amount of 0.1 to 50 wt. %, preferably 1 to 20 wt. %, morepreferably 1 to 10 wt. %, based on the total amount of the electrolyticsolution.

Cyanoalkanoic Acid Ester Compound

The cyanoalkanoic acid ester compound preferably has an alkylene groupof 2-18 carbon atoms (particularly 4-12 carbon atoms). The alkylenegroup can be linear or branched.

Examples of the cyanoalkanoic acid ester compounds include linearcompounds such as methyl 3-cyanopropanoate, methyl 4-cyanobutanoate,methyl 5-cyanopentanoate, methyl 6-cyanohexanoate, methyl7-cyanoheptanoate, methyl 8-cyanooctanoate, methyl 9-cyanononanoate,methyl 10-cyanodecanoate, methyl 11-cyanoundecanoate, and methyl12-cyanododecanoate, and branched compounds such as methyl7-cyanoundecanoate and methyl 2-butyl-7-cyanoheptanoate. The ester isnot limited to the methyl ester, and ethyl ester, propyl ester andphenyl ester can be also employed.

The cyanoalkanoic acid ester compound is generally contained in theelectrolytic solution in an amount of 0.01 to 50 wt. %, preferably 0.1to 40 wt. %, more preferably 1 to 20 wt. %, based on the total amount ofthe electrolytic solution.

[Monocarboxylic acid having an alkyl chain of 3-7 carbon atoms and twoalkyl groups of 1-4 carbon atoms at the β-position of the carboxyl groupand salts thereof]

This monocarboxylic acid is a compound having the formula of (R¹) (R²)(R³) CH₂COOH [each of R¹, R², and R³ independently is an alkyl grouphaving 1 to 4 carbon atoms].

Each of R¹, R², and R³ of the monocarboxylic acid represented by theabove-mentioned formula independently is an alkyl group having 1 to 4carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, or tert-butyl. Methyl or ethyl is preferred.

Examples of the monocarboxylic acids of the above-mentioned formulainclude 3,3-dimethylbutanoic acid (R¹═R²═R³=methyl),3,3-dimethylpentanoic acid (R¹═R²=methyl, R³=ethyl), 3,3-diethylbutanoicacid (R¹═R²=ethyl, R³=methyl), 3,3-diethylpentanoic acid(R¹═R²═R³=ethyl), and 3,3,4-trimethylpentanoic acid (R¹=R²═methyl,R³=isopropyl). Examples of salts of the monocarboxylic acids are saltsof the aforementioned organic bases.

The above-mentioned monocarboxylic acid or a salt thereof is generallycontained in the electrolytic solution in an amount of 0.1 to 50 wt. %,preferably 1 to 40 wt. %, more preferably 1 to 20 wt. %, based on thetotal amount of the electrolytic solution.

Monocarboxylic acid having an alkyl chain of 3-7 Carbon atoms and oneethyl group at the α-position of the carboxyl group, and salts thereof]

Examples of the monocarboxylic acids include 2-ethylbutanoic acid,2-ethylpentanoic acid, 2-ethylhexanoic acid, and 2-ethylheptanoic acid.Examples of salts of the monocarboxylic acids are salts of theaforementioned organic bases.

The above-mentioned monocarboxylic acid or a salt thereof is generallycontained in the electrolytic solution in an amount of 0.1 to 50 wt. %,preferably 1 to 40 wt. %, more preferably 1 to 20 wt. %, based on thetotal amount of the electrolytic solution.

[Monocarboxylic acid of a cyclic saturated compound having 5 or 6ring-forming carbon atoms, and salts thereof]

Examples of the monocarboxylic acids include cyclopentanecarboxylic acidand cyclohexanecarboxylic acid. Examples of salts of the monocarboxylicacids are salts of the aforementioned organic bases.

The above-mentioned monocarboxylic acid or a salt thereof is generallycontained in the electrolytic solution in an amount of 0.1 to 50 wt. %,preferably 1 to 40 wt. %, more preferably 1 to 20 wt. %, based on thetotal amount of the electrolytic solution.

Optionally Employable Other Additives

Into an electrolytic solution for electrolytic capacitors according tothe invention, one or more of acidic alkyl phosphate esters, phosphoricacid, and phosphorous acid which can inhibit hydrolytic deterioration ofan anode oxide film (which occurs in a long term storage of a capacitor)and increase of leakage current of a capacitor can be incorporated. Theacidic alkyl phosphate esters, phosphoric acid, or phosphorous acid canbe incorporated into the electrolytic solution in an amount of 0.02 to 4wt. %, based on the total amount of the electrolytic solution.

Further, one or more aromatic nitro compounds such as o-nitrophenol,m-nitrophenol, p-nitrophenol, and m-nitroacetophenone which have afunction to inhibit increase of the internal pressure caused by hydrogengas generated inside of a capacitor can be added. The amount of thearomatic nitro compound preferably in the range of 0.02 to 6 wt. %,based on the total amount of the electrolytic solution.

The present invention is further described by the following examples. Inthe following examples, the electrolytic solution was prepared bydissolving one or more additives in an aqueous organic solventcomprising water and ethylene glycol (or a combination of ethyleneglycol and γ-butyrolactone). In the electrolytic solution was placed analuminum foil. A constant current of a current density of 10 mA/cm² wasapplied to this system. Then, a spark voltage (V), a period of time toreach 400 V (working period (chemical conversion period): minutes), andan electroconductance at 20° C. (specific conductance mS/cm) weremeasured. The measured values are described below.

Further, electrolytic solutions having a known representativecomposition were also subjected to the same measurement. The measuredvalues are also described below.

COMPARISON EXAMPLE 1

Ammonium 1,6-decanedicarboxylate (15 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 430 V

Working period: 4.8 minutes

Electroconductance: 2.1 mS/cm

COMPARISON EXAMPLE 2

Ammonium pivalate (15 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 440 V

Working period: 5.6 minutes

Electroconductance: 2.2 mS/cm

EXAMPLE 1

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 475 V

Working period: 5.4 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 2

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (52 wt. %)

Adiponitrile (30 wt. %)

Water (3 wt. %)

Spark voltage: 520 V

Working period: 5.6 minutes

Electroconductance: 1.6 mS/cm

EXAMPLE 3

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (81 wt. %)

Adiponitrile (1 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 5.2 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 4

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (72 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 5.4 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 5

Ammonium 1,6-decanedicarboxylate (7.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (72 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 495 V

Working period: 5.1 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 6

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ammonium pivalate (5 wt. %)

Ethylene glycol (72 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 4.8 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 7

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (60 wt. %)

1,5-Pentanediol (12 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 5.6 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 8

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (60 wt. %)

1,2,4-Butanetriol (12 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 5.4 minutes

Electroconductance: 1.3 mS/cm

EXAMPLE 9

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (60 wt. %)

1,2-Butanediol (12 wt. %)

1,6-Dicyanodecane (10 wt. %)

Water (3 wt. %)

Spark voltage: 495 V

Working period: 5.5 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 10

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (60 wt. %)

Diethylene glycol (12 wt. %)

1,6-Dicyanodecane (10 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 5.4 minutes

Electroconductance: 1.3 mS/cm

EXAMPLE 11

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (60 wt. %)

Pinacol (12 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 515 V

Working period: 6.2 minutes

Electroconductance: 1.1 mS/cm

EXAMPLE 12

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (70 wt. %)

Adiponitrile (17 wt. %)

Water (3 wt. %)

Spark voltage: 560 V

Working period: 6.1 minutes

Electroconductance: 0.8 mS/cm

EXAMPLE 13

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (22 wt. %)

γ-Butyrolactone (50 wt. %)

Adiponitrile (15 wt. %)

Water (3 wt. %)

Spark voltage: 560 V

Working period: 6.0 minutes

Electroconductance: 0.9 mS/cm

EXAMPLE 14

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (73 wt. %)

Adiponitrile (15 wt. %)

Water (2 wt. %)

Spark voltage: 500 V

Working period: 4.6 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 15

Ammonium pivalate (10 wt. %)

Ethylene glycol (73 wt. %)

Adiponitrile (15 wt. %)

Water (2 wt. %)

Spark voltage: 510 V

Working period: 5.4 minutes

Electroconductance: 2.0 mS/cm

Comparisons between the results of Examples 1 to 15 and the results ofComparison Examples 1 to 2 indicate that the electrolytic solutionscontaining additives of ammonium 1,6-decanedicarboxylate (or ammoniumpivalate) and a nitrile compound according to the invention give anapparently high spark voltage as compared with the electrolyticsolutions containing an additive of ammonium 1,6-decanedicarboxylatealone, while almost no changes are observed on the working period andelectroconductivity. Similar results are also observed in theelectrolytic solution containing additives of ammonium1,6-decanedicarboxylate and ammonium pivalate in combination.

The following examples show the results measured on the performances ofthe electrolytic solution to indicate the difference between the caseusing a commercially available ammonium 1,6-decanedicarboxylate forindustrial use (containing 6 wt. % of ammonium 1,10-decanedicarboxylateas impurities) and the case using a high purity ammonium1,6-decanedicarboxylate (containing 0.1 wt. % of ammonium1,10-decanedicarboxylate). A high purity 1,6-decanedicarboxylic acid forthe high purity ammonium 1,6-decanedicarboxylate was prepared by thefollowing method.

Preparation of High Purity 1,6-Decanedicarboxylic Acid

1,6-Decanedicarboxylic acid obtained as that for industrial use(containing 6 wt. % of 1,10-decanedicarboxylic acid as impurities) wasconverted into its methyl ester. The methyl ester product was subjectedto rectification under the conditions of a reflux ratio of 1 and atheoretical plate number of 20 to separate methyl1,10-decanedicarboxylate (b.p.: 165° C./10 mmHg) from methyl1,6-decanedicarboxylate (b.p.: 156° C./10 mmHg). Subsequently, methyl1,6-decanedicarboxylate was hydrolyzed to obtain the high purity1,6-decanedicarboxylic acid (containing 0.1 wt. % of1,10-decanedicarboxylic acid).

In the following examples, the electrolytic solution was prepared bydissolving one or more additives in an aqueous organic solventcomprising water and ethylene glycol. In the electrolytic solution wasplaced an aluminum foil. A constant current of a current density of 10mA/cm² was applied to this system. Then, the spark voltage (V), a periodof time to reach 400 V (working period: minutes), and anelectroconductance at 20° C. (specific conductance) were measured.Further, a ratio (%) of decrease of electroconductance after keeping theelectrolytic solution at 105° C. for 720 hours was measured.

The measured values are described below.

COMPARISON EXAMPLE 3

Ammonium 1,6-decanedicarboxylate (for industrial use, 15 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 430 V

Working period: 4.8 minutes

Electroconductance: 2.1 mS/cm

Ratio of decrease of conductance: 31%

EXAMPLE 16

Ammonium 1,6-decanedicarboxylate (for industrial use, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 475 V

Working period: 5.4 minutes

Electroconductance: 1.7 mS/cm

Ratio of decrease of conductance: 18%

EXAMPLE 17

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 5.3 minutes

Electroconductance: 1.7 mS/cm

Ratio of decrease of conductance: 17%

EXAMPLE 18

Ammonium 1,6-decanedicarboxylate (for industrial use, 7.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 5.0 minutes

Electroconductance: 1.8 mS/cm

Ratio of decrease of conductance: 21%

EXAMPLE 19

Ammonium 1,6-decanedicarboxylate (high purity, 7.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 485 V

Working period: 4.9 minutes

Electroconductance: 1.8 mS/cm

Ratio of decrease of conductance: 19%

EXAMPLE 20

Ammonium 1,6-decanedicarboxylate (for industrial use, 10 wt. %)

Ammonium pivalate (5 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 470 V

Working period: 4.7 minutes

Electroconductance: 1.7 mS/cm

Ratio of decrease of conductance: 26%

EXAMPLE 21

Ammonium 1,6-decanedicarboxylate (high purity, 10 wt. %)

Ammonium pivalate (5 wt. %)

Ethylene glycol (82 wt. %)

Water (3 wt. %)

Spark voltage: 475 V

Working period: 4.6 minutes

Electroconductance: 1.8 mS/cm

Ratio of decrease of conductance: 22%

EXAMPLE 22

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (70 wt. %)

1,5-Pentanediol (12 wt. %)

Water (3 wt. %)

Spark voltage: 475 V

Working period: 5.3 minutes

Electroconductance: 1.4 mS/cm

Ratio of decrease of conductance: 17%

EXAMPLE 23

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (70 wt. %)

1,2,4-Butanetriol (12 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 4.8 minutes

Electroconductance: 1.3 mS/cm

Ratio of decrease of conductance: 16%

EXAMPLE 24

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (70 wt. %)

1,2-Butanediol (12 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 5.2 minutes

Electroconductance: 1.5 mS/cm

Ratio of decrease of conductance: 16%

EXAMPLE 25

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (70 wt. %)

Diethylene glycol (12 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 4.7 minutes

Electroconductance: 1.5 mS/cm

Ratio of decrease of conductance: 16%

EXAMPLE 26

Ammonium 1,6-decanedicarboxylate (high purity, 5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (70 wt. %)

Pinacol (12 wt. %)

Water (3 wt. %)

Spark voltage: 485 V

Working period: 5.9 minutes

Electroconductance: 1.1 mS/cm

Ratio of decrease of conductance: 14%

Comparisons between the results of Examples 16 to 26 and the results ofComparison Example 3 indicate that the electrolytic solutions employinga high purity ammonium 1,6-decanedicarboxylate (which is prepared bypurifying ammonium 1,6-decanedicarboxylate for industrial use todecrease content of ammonium 1,10-decanedicarboxylate) give a high sparkvoltage and a low radio of decrease of conductance as compared with theelectrolytic solution employing ammonium 1,6-decanedicarboxylate forindustrial use.

In the following examples, the electrolytic solution was prepared bydissolving ammonium 1,6-decanedicarboxylate and a diester compound (or alactone compound having an alkyl group, or a cyanoalkane compound) in anaqueous organic solvent comprising water and ethylene glycol. In theelectrolytic solution was placed an aluminum foil. A constant current ofa current density of 10 mA/cm² was applied to this system. Then, thespark voltage (V), a period of time to reach 400 V (working period:minutes), and an electroconductance at 20° C. (specific conductance)were measured. The measured values are described below.

COMPARISON EXAMPLE 4

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 440 V

Working period: 5.4 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 27

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (77 wt. %)

Dimethyl adipate (10 wt. %)

Water (3 wt. %)

Spark voltage: 470 V

Working period: 4.6 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 28

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (84 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 4.5 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 29

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (77 wt. %)

Methyl 11-cyanoundecanoate (10 wt. %)

Water (3 wt. %)

Spark voltage: 475 V

Working period: 4.7 minutes

Electroconductance: 1.3 mS/cm

EXAMPLE 30

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (82 wt. %)

γ-Nonanolactone (5 wt. %)

Water (3 wt. %)

Spark voltage: 465 V

Working period: 4.7 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 31

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (74 wt. %)

γ-Undecanolactone (3 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 4.7 minutes

Electroconductance: 1.3 mS/cm

EXAMPLE 32

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 11-cyanoundecanoate (5 wt. %)

Ethylene glycol (84 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 8.8 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 33

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ammonium pivalate (5 wt. %)

Ethylene glycol (79 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 485 V

Working period: 4.8 minutes

Electroconductance: 1.6 mS/cm

EXAMPLE 34

Ammonium 1,6-decanedicarboxylate (7.5 wt. %)

Ammonium pivalate (7.5 wt. %)

Ethylene glycol (79 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 5.1 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 35

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (79 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 505 V

Working period: 5.2 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 36

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (54 wt. %)

γ-Butyrolactone (25 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 505 V

Working period: 4.9 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 37

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (69 wt. %)

Methyl 11-cyanoundecanoate (10 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 495 V

Working period: 4.9 minutes

Electroconductance: 1.6 mS/cm

EXAMPLE 38

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium pivalate (10 wt. %)

Ethylene glycol (69 wt. %)

Adiponitrile (10 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 5.0 minutes

Electroconductance: 1.7 mS/cm

EXAMPLE 39

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 2,2-diisopropylpropanoate (10 wt. %)

Ethylene glycol (39 wt. %)

γ-Undecanolactone (3 wt. %)

γ-Butyrolactone (25 wt. %)

Adiponitrile (15 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 4.9 minutes

Electroconductance: 1.8 mS/cm

Comparisons between the results of Examples 27 to 39 and the results ofComparison Example 4 indicate that the electrolytic solutions containingadditives of ammonium 1,6-decanedicarboxylate and a diester compound (ora lactone compound having an alkyl group or a cyanoalkane compound,optionally further a nitrile compound) according to the invention givean apparently high spark voltage as compared with the electrolyticsolutions containing an additive of ammonium 1,6-decanedicarboxylatealone, while almost no changes are observed on the working period andelectroconductivity.

In the following examples, the electrolytic solution was prepared bydissolving ammonium 1,6-decanedicarboxylate and a monocarboxylic acidhaving an alkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4carbon atoms at the β-position of the carboxyl group (or its salt) in anaqueous organic solvent comprising ethylene glycol (or a combination ofethylene glycol and γ-butyrolactone) and water. In the electrolyticsolution was placed an aluminum foil. A constant current of a currentdensity of 10 mA/cm² was applied to this system. Then, the spark voltage(V), a period of time to reach 400 V (working period: minutes), and anelectroconductance at 20° C. (specific conductance) were measured. Themeasured values are described below.

EXAMPLE 40

Ammonium 1,6-decanedicarboxylate (7.5 wt. %)

Ammonium 3,3-dimethylbutanoate (2.5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 5.7 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 41

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 3,3-dimethylbutanoate (5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 500 V

Working period: 6.0 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 42

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium 3,3-dimethylbutanoate (7.5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 6.2 minutes

Electroconductance: 1.6 mS/cm

EXAMPLE 43

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium 3,3-dimethylbutanoate (7.5 wt. %)

Ethylene glycol (70 wt. %)

Adiponitrile (17 wt. %)

Water (3 wt. %)

Spark voltage: 550 V

Working period: 6.1 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 44

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium 3,3-dimethylbutanoate (7.5 wt. %)

Ethylene glycol (22 wt. %)

γ-Butyrolactone (50 wt. %)

Adiponitrile (15 wt. %)

Water (3 wt. %)

Spark voltage: 560 V

Working period: 5.8 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 45

Ammonium 1,6-decanedicarboxylate (2.5 wt. %)

Ammonium 3,3-dimethylbutanoate (7.5 wt. %)

Ethylene glycol (17 wt. %)

γ-Butyrolactone (50 wt. %)

γ-Undecanolactone (5 wt. %)

Adiponitrile (15 wt. %)

Water (3 wt. %)

Spark voltage: 560 V

Working period: 5.3 minutes

Electroconductance: 1.5 mS/cm

Comparisons between the results of Examples 40 to 45 and the results ofComparison Example 4 indicate that the electrolytic solutions containingadditives of ammonium 1,6-decanedicarboxylate and a monocarboxylic acidhaving an alkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4carbon atoms at the β-position of the carboxyl group or its salt(optionally further a nitrile compound) according to the invention givean apparently high spark voltage as compared with the electrolyticsolutions containing an additive of ammonium 1,6-decanedicarboxylatealone, while almost no changes are observed on the working period andelectroconductivity.

In the following examples, the electrolytic solution was prepared bydissolving ammonium 1,6-decanedicarboxylate and a monocarboxylic acidhaving an alkyl chain of 3-7 carbon atoms and one ethyl group at theα-position of the carboxyl group (or its salt) or a monocarboxylic acidof a cyclic saturated compound having 5 or 6 ring-forming carbon atoms(or its salt) in an aqueous organic solvent comprising ethylene glycoland water. In the electrolytic solution was placed an aluminum foil. Aconstant current of a current density of 10 mA/cm² was applied to thissystem. Then, the spark voltage (V), a period of time to reach the sparkvoltage (working period: minutes), and an electroconductance at 20° C.(specific conductance) were measured. The measured values are describedbelow.

COMPARISON EXAMPLE 5

Ammonium 1,6-decanedicarboxylate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 440 V

Working period: 5.7 minutes

Electroconductance: 1.4 mS/cm

COMPARISON EXAMPLE 6

Ammonium 2-ethylbutanoate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 330 V

Working period: 9.2 minutes

Electroconductance: 1.6 mS/cm

COMPARISON EXAMPLE 7

Ammonium 2-ethylhexanoate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 355 V

Working period: 12.2 minutes

Electroconductance: 1.0 mS/cm

COMPARISON EXAMPLE 8

Ammonium 2-cyclopentanoate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 405 V

Working period: 13.2 minutes

Electroconductance: 1.6 mS/cm

COMPARISON EXAMPLE 9

Ammonium 2-cyclohexanoate (10 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 480 V

Working period: 18.9 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 46

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 2-ethylbutanoate (5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 490 V

Working period: 5.6 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 47

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 2-ethylhexanoate (5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 520 V

Working period: 6.5 minutes

Electroconductance: 1.3 mS/cm

EXAMPLE 48

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium cyclopentanoate (5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 495 V

Working period: 6.2 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 49

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium cyclohexanoate (5 wt. %)

Ethylene glycol (87 wt. %)

Water (3 wt. %)

Spark voltage: 495 V

Working period: 6.0 minutes

Electroconductance: 1.4 mS/cm

EXAMPLE 50

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 2-ethylhexanoate (5 wt. %)

Ethylene glycol (77 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 520 V

Working period: 5.9 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 51

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium 2-ethylhexanoate (5 wt. %)

Ethylene glycol (74 wt. %)

Adiponitrile (10 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 530 V

Working period: 5.9 minutes

Electroconductance: 1.5 mS/cm

EXAMPLE 52

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium cyclohexanoate (5 wt. %)

Ethylene glycol (77 wt. %)

Adiponitrile (10 wt. %)

Water (3 wt. %)

Spark voltage: 510 V

Working period: 5.9 minutes

Electroconductance: 1.6 mS/cm

EXAMPLE 53

Ammonium 1,6-decanedicarboxylate (5 wt. %)

Ammonium cyclohexanoate (5 wt. %)

Ethylene glycol (74 wt. %)

Adiponitrile (10 wt. %)

γ-Undecanolactone (3 wt. %)

Water (3 wt. %)

Spark voltage: 520 V

Working period: 5.9 minutes

Electroconductance: 1.6 mS/cm

Comparisons between the results of Examples 46 to 53 and the results ofComparison Examples 4 to 9 indicate that the electrolytic solutionscontaining additives of ammonium 1,6-decanedicarboxylate and amonocarboxylic acid having an alkyl chain of 3-7 carbon atoms and oneethyl group at the α-position of the carboxyl group or its salt or amonocarboxylic acid of a cyclic saturated compound having 5 or 6ring-forming carbon atoms or its salt (optionally further a nitrilecompound) according to the invention give an apparently high sparkvoltage as compared with the electrolytic solutions containing anadditive of ammonium 1,6-decanedicarboxylate alone, while almost nochanges are observed on the working period and electroconductivity.

UTILIZATION IN INDUSTRY

The electrolytic solutions and electrolytic capacitors of the inventionare favorably employable as driving power supplies for air conditioners,refrigerators, microwave ovens, washing machines, illuminators,elevators, robots, NC machine tools, electric trains, solar generators,hybrid motor cars and electric motor cars.

What is claimed is:
 1. An electrolytic solution comprising water and awater-miscible organic solvent, which further contains1,6-decanedicarboxylic acid or a salt thereof and at least one additiveselected from the group consisting of a dinitrile compound, pivalic acidor a salt thereof, a diester compound, a lactone compound having analkyl group, a cyanoalkanoic acid ester, a monocarboxylic acid having analkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4 carbon atomsat the β-position of the carboxyl group, a salt thereof, amonocarboxylic acid having an alkyl chain of 3-7 carbon atoms and oneethyl group at the α-position of the carboxyl group, a salt thereof, amonocarboxylic acid of a cyclic saturated compound having 5 or 6ring-forming carbon atoms, and a salt thereof.
 2. The electrolyticsolution of claim 1, wherein the water-miscible organic solvent is anorganic solvent containing ethylene glycol.
 3. The electrolytic solutionof claim 1, which contains as the additive 0.1 to 50 wt. % of adinitrile compound comprising an alkylene chain of 1-12 carbon atoms andtwo nitrile groups attached to the alkylene chain.
 4. The electrolyticsolution of claim 3, which further contains as the additive 1 to 20 wt.% of pivalic acid or a salt thereof.
 5. The electrolytic solution ofclaim 1, which contains as the additive 1 to 20 wt. % of pivalic acid ora salt thereof.
 6. The electrolytic solution of claim 5, in which aweight ratio of pivalic acid or a salt thereof to 1,6-decanedicarboxylicacid or a salt thereof is in the range of 25/75 to 90/10.
 7. Theelectrolytic solution of claim 1, which contains as the additive 0.01 to50 wt. % of a diester compound having an alkylene group of 2-18 carbonatoms.
 8. The electrolytic solution of claim 7, which further containsas the additive 1 to 20 wt. % of pivalic acid or a salt thereof.
 9. Theelectrolytic solution of claim 1, which contains as the additive 0.1 to50 wt. % of a lactone compound having at least one alkyl group of 1-12carbon atoms.
 10. The electrolytic solution of claim 9, which furthercontains as the additive 1 to 20 wt. % of pivalic acid or a saltthereof.
 11. The electrolytic solution of claim 1, which contains as theadditive 0.01 to 50 wt. % of a cyanoalkanoic acid ester having analkylene group of 2-18 carbon atoms.
 12. The electrolytic solution ofclaim 11, which further contains as the additive 1 to 20 wt. % ofpivalic acid or a salt thereof.
 13. The electrolytic solution of claim1, which contains as the additive 0.1 to 50 wt. % of a monocarboxylicacid having an alkyl chain of 3-7 carbon atoms and two alkyl groups of1-4 carbon atoms at the β-position of the carboxyl group or a saltthereof.
 14. The electrolytic solution of claim 13, which furthercontains as the additive 0.1 to 50 wt. % of a dinitrile compound. 15.The electrolytic solution of claim 1, which contains as the additive amonocarboxylic acid having an alkyl chain of 3-7 carbon atoms and oneethyl group at the α-position of the carboxyl group or a salt thereof,under the condition that a total amount of the monocarboxylic acid orsalt and 1,6-decanedicarboxylic acid or a salt thereof is 1 to 20 wt. %.16. The electrolytic solution of claim 15, which further contains as theadditive 0.1 to 50 wt. % of a dinitrile compound.
 17. The electrolyticsolution of claim 1, which contains as the additive a monocarboxylicacid of a cyclic saturated compound having 5 or 6 ring-forming carbonatoms or a salt thereof, under the condition that a total amount of themonocarboxylic acid or salt and 1,6-decanedicarboxylic acid or a saltthereof is 1 to 20 wt. %.
 18. The electrolytic solution of claim 17,which further contains as the additive 0.1 to 50 wt. % of a dinitrilecompound.
 19. An electrolytic solution comprising water and awater-miscible organic solvent, which further contains a carboxylic acidor a salt thereof and at least one additive selected from the groupconsisting of a dinitrile compound, a diester compound, a lactonecompound having an alkyl group, and a cyanoalkanoic acid ester.
 20. Theelectrolytic solution of claim 19, wherein the water-miscible organicsolvent is an organic solvent containing ethylene glycol.
 21. Theelectrolytic solution of claim 19, which contains as the additive 0.1 to50 wt. % of a dinitrile compound comprising an alkylene chain of 1-12carbon atoms and two nitrile groups attached to the alkylene chain. 22.The electrolytic solution of claim 19, which contains as the additive0.01 to 50 wt. % of a diester compound having an alkylene group of 2-18carbon atoms.
 23. The electrolytic solution of claim 19, which containsas the additive 0.1 to 50 wt. % of a lactone compound having at leastone alkyl group of 1-12 carbon atoms.
 24. The electrolytic solution ofclaim 19, which contains as the additive 0.01 to 50 wt. % of acyanoalkanoic acid ester having an alkylene group of 2-18 carbon atoms.25. An electrolytic capacitor comprising a metallic element having anoxide film on a surface thereof and an electrolytic solution in a sealedcase, wherein the electrolytic solution comprises water and awater-miscible organic solvent, which further contains1,6-decanedicarboxylic acid or a salt thereof and at least one additiveselected from the group consisting of a dinitrile compound, pivalic acidor a salt thereof, a diester compound, a lactone compound having analkyl group, a cyanoalkanoic acid ester, a monocarboxylic acid having analkyl chain of 3-7 carbon atoms and two alkyl groups of 1-4 carbon atomsat the β-position of the carboxyl group, a salt thereof, amonocarboxylic acid having an alkyl chain of 3-7 carbon atoms and oneethyl group at the α-position of the carboxyl group, a salt thereof, amonocarboxylic acid of a cyclic saturated compound having 5 or 6ring-forming carbon atoms, and a salt thereof.
 26. The electrolyticcapacitor of claim 25, wherein the metallic member is an aluminum foil.27. An electrolytic capacitor comprising a metallic member having anoxide film on a surface thereof and an electrolytic solution in a sealedcase, wherein the electrolytic solution comprises water and awater-miscible organic solvent, which further contains a carboxylic acidor a salt thereof and at least one additive selected from the groupconsisting of a dinitrile compound, a diester compound, a lactonecompound having an alkyl group, and a cyanoalkanoic acid ester.
 28. Theelectrolytic capacitor of claim 27, wherein the metallic member is analuminum foil.